How do I install Mira_Tools addon?
From the information available on the Mira-Tools Wiki page:


Download the zip archive for the development version.
Unzip the downloaded file.
Copy mira_tools/blender/addons/mira_tools folder into your user addons folder.
Refresh Blender's add-ons and enable the add-on "MiraTools".


Apparently the ZIP they ship contains all kinds of data, it's not just a Blender add-on. This means that you cannot install it via Blender itself, but have to do it manually. Their issue #22 also complains about this.